NEW YORK — Law enforcement officials have announced the arrest of 31 people who they said had been involved in running an international prostitution ring that operated a Korean-owned brothel network in the Northeast United States.

Officials said Wednesday that they also took 67 young South Korean women into protective custody, all of whom they believe were brought to the United States illegally and forced to work as prostitutes, victims of human trafficking.

Many of the houses in what officials described as a "network of Korean- owned brothels stretching from Rhode Island to Washington, D.C." claimed to be legitimate businesses like massage parlors, health spas and acupuncture clinics.

"This exploitation is not a back-alley business," said Michael Garcia, chief federal prosecutor in Manhattan. "It happens in residential areas of our nation's capital, it happens in the West 20's in New York City."

The 19 brothels catered chiefly to Asian customers who learned about the illicit services through word of mouth, officials said. Some of the houses were making tens of thousands of dollars a month, officials said.

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The ring's recruiters in South Korea sought women who wanted to come to the United States, officials said. The women were then given false documents or smuggled across the border from Mexico or Canada.

Drivers carried the women from a point of entry to a brothel, and sometimes moved them between brothels within the network, officials said. Once the women were delivered to a brothel, officials said, managers would typically take away their identification and travel documents and threaten to turn them in to the authorities or hurt their relatives in South Korea if they tried to leave. The women were forced to work to pay off tens of thousands of dollars of debt they had accumulated in their travel from South Korea, officials said.

Some of the brothels had special rooms or compartments where the women were hidden in case of a raid, officials said.

The arrests are connected to the breakup of a brothel operation in March in New York. In that case, an undercover police detective discovered that the operation flourished because the owners had bribed two veteran police officers. Those officers were charged with public corruption and are awaiting federal prosecution.